How Four Discoveries Changed Lives

Jonas Salk and the Polio Vaccine

An information text written for this worksheet. Polio is a disease caused by a virus. It can make muscles weak and sometimes leaves people unable to walk or to breathe on their own. In the early 1950s, polio struck tens of thousands of Americans every year, most of them children. Many families kept their children away from swimming pools and summer camps, afraid of catching it. Jonas Salk, an American doctor and scientist, made a vaccine to protect people from polio. In 1954, more than a million children took part in a test of the vaccine. In April 1955 the vaccine was announced as safe and effective. Salk did not patent it, so it could be made widely. Within a few years, polio cases in the United States fell sharply.

Louis Pasteur and Safer Milk

An information text written for this worksheet. In the 1800s, milk and other foods often spoiled quickly, and milk could carry germs that made people, especially young children, very sick. Louis Pasteur, a French scientist, showed in the 1860s that tiny living things called microbes make food spoil. He found that heating a liquid such as wine for a short time, without boiling it, and then cooling it, killed most of the harmful microbes without ruining the taste. This method is named pasteurization, after him. Later, cities in Europe and the United States began to require that milk be pasteurized. Fewer children became sick from milk, and milk stayed fresh for longer, so it could be shipped farther.